Objectives

The Women's Health Initiative (WHI) is a long-term national health study that has focused on strategies for preventing heart disease, breast and colorectal cancer, and osteoporotic fractures in postmenopausal women. These chronic diseases are the major causes of death, disability, and frailty in older women of all races and socioeconomic backgrounds.

Background

The Women's Health Initiative (WHI) is a long-term national health study that has focused on strategies for preventing heart disease, breast and colorectal cancer, and osteoporotic fractures in postmenopausal women. These chronic diseases are the major causes of death, disability, and frailty in older women of all races and socioeconomic backgrounds.

Background (Background information about the study):
The WHI had two major parts: a randomized Clinical Trial and an Observational Study. The randomized controlled Clinical Trial (CT) enrolled 68,132 postmenopausal women between the ages of 50-79 into trials testing three prevention strategies. If eligible, women could choose to enroll in one, two, or all three of the trial components. The components are:

• Hormone Therapy Trials (HT): This component examined the effects of combined hormones or estrogen alone on the prevention of coronary heart disease and osteoporotic fractures, and associated risk for breast cancer. Women participating in this component took hormone pills or a placebo (inactive pill) until the Estrogen plus Progestin and Estrogen Alone trials were stopped early in July 2002 and March 2004, respectively. All HT participants continued to be followed without intervention until close-out.

• Dietary Modification Trial (DM): The Dietary Modification component evaluated the effect of a low-fat and high fruit, vegetable and grain diet on the prevention of breast and colorectal cancers and coronary heart disease. Study participants followed either their usual eating pattern or a low-fat dietary pattern.

• Calcium/Vitamin D Trial (CaD): This component began 1 to 2 years after a woman joined one or both of the other clinical trial components. It evaluated the effect of calcium and vitamin D supplementation on the prevention of osteoporotic fractures and colorectal cancer. Women in this component took calcium and vitamin D pills or a placebo.

The Observational Study (OS) is examining the relationship between lifestyle, health and risk factors and specific disease outcomes. This component involves tracking the medical history and health habits of 93,676 women. Recruitment for the observational study was completed in 1998 and participants were followed for 8 to 12 years.

WHI Extension Studies continued follow-up of consenting participants, the first consenting participants from each of the original WHI study components for an additional five years (2005-2010) of follow-up, and the second consenting participants from the first Extension Study for an additional five years (2010-2015). Annual updates on health outcomes are collected by mail from the participants enrolled in each Extension Study. See WHI Timeline for WHI and the Extension Studies.

Participants

Subjects were postmenopausal women aged 50-79 with minimal exclusion criteria.